| Nowadays, the heavy commercial transport vehicle is playing an important role in thecountry modern infrastructure, and its driving cycles are complicated and varied. It oftenencounters the problem of insufficient traction ability when driving in bad road like muddyroad, also has the phenomenon of overheated and worn seriously brake when frequent braking.The current technology including all-wheels drive mechanically and retarder braking device,although, can obviously solve the prolem, yet they have the weakness like laege dead load,energy wasting and fuel consumption increasing and so on.Therefore, based on the Natural Science Foundation of China as well as cooperation withan enterprise, and considering the structure of one heavy tractor, the hydraulic hub-motorauxiliary system (HHMAS) is proposed in this paper. The HHMAS not only can apparentlyimprove the passing ability of vehicle driving in the bad road, but also can recycle the kineticenergy of braking vehicle, as well as reduce the use of brake. In addition, there’s little researchon this theme in domestic, and the system costs less, the hydraulic units have small bulk andlight weight, which make the system good application prospect in the market for the heavycommercial vehicles.Around the HHMAS, its structure, auxiliary control strategy and verification, dynamicmodel and other aspects have been researched as follows.(1) The power transfer paths of the HHMAS in different operating mode, and theinstallation position of the power take off are described in this paper. What’s more, thestructure of the hydraulic valve block (VB) is analyzed in detail. Based on the existingcondition of the Research Group, as well as cooperation with an enterprise, the structure of aprototype VB, which is used in the auxiliary drive scheme, is supposed and verified through the experimental results, and on this basis, the structure scheme of the VB in the HHMAS isdesigned and analyzed.(2) In the aspect of the system dynamics, the modeling method of the mechanicaltransmission system (MTS) and the hydraulic transmission system (HTS) are analyzed in thispaper. Furtherly, the math models of the MTS and HTS are built respectively in theenvironment of AMESIM and MATLAB, both can comuunicate with the s-funciton module,then the simulaiton model of the whole sysem is established in this paper.(3) According to the construct of the HHMAS, in the aspect of the auxiliary drive control,the mode switch logic considering the engineering application is proposed, and the controlmethod of VB and pump displacement in the operation mode of free wheel, creep drive andassistant drive are researched in this paper. In the aspect of the auxiliary brake control,considering the system feature, the start and stop logic for the auxiliary brake is proposed.Meanwhile, focused on the least change of original vehicle brake performance, the allocatedstrategy of the auxiliary brake torque is researched.(4) Based on simulation models of the HHMAS, the simulation tests for the pumpdisplacement controling algorithm, the auxiliary drive and brake control strategy areconducted, and the results proved the feasibility and validity of the control strategy, whichestablishes the foundation for the future development of the HHMAS. |
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